Forced circulation cooling apparatus for continuous strip furnaces



Nov. 2, 1954 Filed June 6, 1951 A. H. VAUGHAN FORCED CIRCULATION COOLINGAPPARATUS FOR CONTINUOUS STRIP FURNACE 5 Sheets-Sheet 1 INVENTOR.

Nov. 2, 1954 A. H. VAUGHAN FORCED CIRCULATION COOLING APPARATUS FORCONTINUOUS STRIP FURNACES 5 Sheets-Sheet 2 Filed June 6, 1951 flrl'lz urfl. Vaughan X 49 26 Z0 Z5 INVENTOR.

ATTORNEYS Nov. 2, 1954 A. H. VAUGHAN 2,693,353

FORCED CIRCULATION COOLING APPARATUS FOR CONTINUOUS STRIP FURNACES FiledJune 6, 1951 Sheets-Sheet 3 9 4 49f $0215 22 I k'iiz zfimi 2a 1 1 1 1 11 1 1 9 1% 1 j 1 I 36 1 31 I I g 5 I x' 1 I 1 1/ 1 -1-- 1 1 1 1 1 1 ,1 1i; 58 {I i \L {/T 1 1 1 42 I *Iqe 5i.

24 26 m 25 zz Z4 49 w m I) U I u v g1 9 C) 22 25 Q Q 45 m 251\ 42INVENTOR. F 5 flrbkzLrHVaugIzan BY aea4g6g41 ATTORNEYS Nov. 2, 1954 A.H. VAUGHAN FORCED CIRCULATION COOLING APPARATUS FOR CONTINUOUS STRIPFURNACES 5 Sheets-Sheet 4 Filed June 6, 1951 m; W m 4% J1 i321! a w A wm w 111i: M 0m W M m u. a A w 7 24 Z0 23 {z 2o 22 INVENTOR.

F29 7 lqwhurlivw mn Nov. 2, 1954 A. H. VAUGHAN FORCED CIRCULATIONCOOLING APPARATUS FOR CONTINUOUS STRIP FURNACES Filed June 6, 1951 5Sheets-Sheet 5 ATTORNEYS Unite States Patent O M FORCED CIRCULATIONCOOLING APPARATUS FOR CONTINUOUS STRIP FURNACES Arthur H. Vaughan,Salem, Ohio, assignor to The Electric Furnace Company, Salem, Ohio, acorporation of Ohio Application June 6, 1951, Serial No. 230,237

5 Claims. (Cl. 266-33) The invention relates generally to a continuousstrip bright annealing furnace and more particularly to forcedcirculation cooling apparatus associated with such a furnace to enable acontinuous strip passing at high speed through the furnace to be cooledrapidly to a'temperature at which it may be safely exposed to theatmosphere without injury to the strip surfaces in completing theannealing operation.

Present day manufacture of strip steel involves high speed rolling andrelated operations and it is desirable that necessary annealingoperations incident to the productilon of finished strip likewise becarried out at high spee For instance, in the production of tinplate itis desired to provide for the continuous bright annealing of the strip,which may be 0.010" thick and 30 or more Wide, at speeds as high as 1000F. P. M. This means that approximately 30 tons of strip will passthrough the furnace every hour.

In performing a desired bright annealing operation at high speed on suchmaterial, it is necessary to continuously heat, soak and first slowlycool the material in a controlled atmosphere for suitable periods oftime to obtain the desired metallurgical results. Then the material maybe rapidly cooled from, say, about 900 F. to a temperature at whichoxidation will not result on exposure of the strip to the atmosphere,say about 200 F. However, it is very difficult to rapidly cool acontinuously moving strip through such a temperature range whentravelling at speeds of the order of 1000 F. P. M. In other words, it ismuch more difficult to cool a rapidly continuously moving strip at ahigh cooling rate than it is to heat the strip at a high heating rate.This is particularly so when the temperature of the strip approachesroom temperature, because of the relatively low temperaturedifferentials involved between the strip temperature and the temperatureof the cooling medium.

Furthermore, space requirements present a problem since under theconditions outlined nearly 1700 feet of strip will be in the heating andcooling chambers of the furnace at any one time, and obviously it wouldbe economically impractical to provide annealing and cooling equipmentnearly one-third of a mile long to handle the material in a continuousone direction pass.

- Accordingly, it is necessary, from a practical standpoint, to providefor the passage of the continuous strip material to and fro or back andforth in loops between conveyor rolls in the heating and coolingchambers of the equipment in order to reduce the size of the equipmentand to conserve space. The back and forth strip travel may beaccomplished by threading the strip either vertically or horizontallythrough the heating and cooling chambers of the equipment. Thisarrangement is very desirable from certain standpoints, but diliicultiesare created thereby in connection with rapidly cooling the strip from,say, 900 F. to 200 F.

Cooling of the rapidly moving strip may be accelerated by using forcedcirculation of a cooling medium. Theoretically, most eiiicient coolingcan be performed by providing for counterflow of the cooling medium withrespect to the direction of strip travel. However, it is not practicalto provide equipment arranged for complete counterflow of cooling mediumthroughout the entire length of strip travel in the cooling chamber ofan annealing furnace because of unbalanced pressures at the entrance andexit ends of the cooling chamber regardless of the path of strip traveltherethrough.

2,693,353 Patented Nov. 2, 1954 Further problems are present in coolingor extracting heat from the cooling medium used in such a forcedcirculation system. This cooling medium, in the case of a continuousbright annealing furnace and in order to avoid oxidation of the stripduring cooling, ordinarily must be the same controlled atmosphere thatis utilized in the furnace heating chambers to avoid oxidation duringheating. Likewise, there is the further problem of avoiding unbalancedpressures in the forced circulation system so as to, on the one hand,avoid loss of the controlled atmosphere, and on the other hand, avoidingress of air to the cooling chambers. Finally, from an economystandpoint, it is desirable to use water as a means of cooling thecooling medium in the forced circulation system.

I have discovered a solution to these complex and interrelated problemswhich involves for each to and fro strip pass, the provision inapparatus for rapidly cooling a continuously moving strip passed to andfro over a series of conveyor rolls in a controlled atmosphere chamber,of a duct through which the strip passes in one direction, of a secondduct spaced from the first duct through which the strip passes in theopposite direction, and of an intermediate duct preferably between thefirst and second ducts. I further provide circulating fan means fordischarging controlled atmosphere cooling medium from one end of theintermediate duct and for drawing it into the other end of said duct. Ifurther provide passages leading from the discharge end of saidintermediate duct to one end of each of the first and second ducts onboth sides of the strip conveyed therethrough; and also passagescommunicating between the intake end of the intermediate duct and theother ends of the first and second ducts on both sides of the strippassing therethrough. Finally, I construct the walls of said ductspreferably as cold plate walls by forming the same either of plate coilmaterial, or as double thickness walls. In each instance Water may becirculated through such walls so that the cooling medium in passingalong the walls at high velocity is thereby rapidly cooled, and in turnrapidly cools the strip in the first and second ducts.

Accordingly, it is a primary object of the present invention to provideforced circulation cooling apparatus for a continuous strip brightannealing furnace in which a strip moving at high speed may be rapidlycooled, particularly during the latter stages of cooling, to atemperature approximating room temperature.

Furthermore, it is an object of the present invention to provide forcedcirculation cooling apparatus for a continuous strip bright annealingfurnace in which strip moving at high speed may be rapidly andefficiently cooled while passing to and fro over a series of conveyorrolls in a controlled atmosphere chamber.

Likewise, it is an object of the present invention to pro: vide improvedforced circulation cooling apparatus for a continuous strip brightannealing furnace in which the strip may be passed through the heatingand cooling stages of the annealing operation at speeds as high as 1000feet per minute in a small sized unit.

Also, it is an object of the present invention to provide forcedcirculation cooling apparatus for a continuous strip bright annealingfurnace in which the continuously moving strip passes to and fro over aseries of conveyor rolls and in which the cooling medium is circulatedat high velocity in a direction contra to the direction of strip travelin about half of the strip passes.

Moreover, it is an object of the present invention to provide forcedcirculation cooling apparatus for a continuous strip bright annealingfurnace in which cooling medium travelling at higli velocity along thestrip surfaces is cooled substantially throughout its path of travel atthe same time that it in turn is cooling the strip.

Furthermore, it is an object of the present invention to provideimproved forced circulation cooling apparatus for a continuous stripbright annealing furnace which eliminates the necessity of conveying thecooling medium out of and reintroducing it into the cooling chamber forcooling the cooling medium.

Likewise, it is an object of the present invention to provide improvedforced circulation cooling apparatus a (a for a continuous strip brightannealing furnace in which pressure differential problems in the coolingmedium circulation system are avoided.

Furthermore, it is an object of the present invention to provide forcedcirculation cooling apparatus for a continuous strip bright annealingfurnace in which water cooled cooling surfaces are located in closeproximity to the strip and the cooling medium is passed at high velocitysimultaneously in contact with both the strip and the cooling surfacesthereby reducing the over-all size of the apparatus to a minimum andobtaining high cooling efficiency.

Finally, it is an object of the present invention to provide newapparatus for rapidly and efficiently cooling continuous moving strippreferably as a component part of a continuous strip bright annealingfurnace which is simple and effective in operation, which overcomes theforegoing difiiculties, which solves long standing problems in the art,and which obtains many new results and advantages herein set forth.

These and other objects and advantages apparent to those skilled in theart from the following description and claims may be obtained, thestated results achieved, and the described difiiculties overcome, by thediscoveries, principles, apparatus, parts, combinations,sub-combinations, elements and methods which comprise the presentinvention, the nature of which is set forth in the following generalstatement, a preferred embodiment of whichillustrative of the best modein which the applicant has contemplated applying the principles-is setforth in the following description, and which are particularly anddistinctly pointed out and set forth in the appended claims forming parthereof.

The nature of the improvements in forced circulation continuous stripcooling apparatus of the present invention may be stated in generalterms as preferably including a cooling chamber, means for continuouslymoving strip material to and fro over a series of conveyor rolls in saidchamber, said chamber being provided with a controlled atmosphere, ductmeans through which the strip is passed in one direction, second ductmeans spaced from the first duct through which the strip is passed inthe opposite direction, an intermediate duct between the first andsecond duct means, circulating fan means for discharging controlledatmosphere cooling medium from one end of the intermediate duct and fordrawing it into the other end of said intermediate duct, passage meanscommunicating between said one end of said intermediate duct and one endof each of the first and second duct means on both sides of the strippassing therethrough, passage means communicating between the other endof the intermediate duct and the other end of each of the first andsecond duct means on both sides of the strip passing therethrough, andcooling surface means on either side of the strip associated with saidfirst and second duct means.

By way of example, a preferred embodiment of improved forced circulationstrip cooling apparatus is illustrated in the accompanying drawingsforming a part hereof, wherein:

Fig. 1 is a diagrammatic side elevation of a preferred arrangement ofimproved cooling apparatus with certain parts broken away and insection;

Fig. 2 is an enlarged fragmentary somewhat diagrammatic sectional viewof the top ends of said certain of the cooling ducts illustrated in Fig.1; V

Fig. 3 is a section looking in the direction of arrows 33, Fig. 2;

Fig. 4 is a view similar to Fig. 2 of an intermediate portion of theducts, illustrating the connections between the ducts and circulatingfans;

Fig. 5 is a view similar to Figs. 2 and 4 showing the bottom ends ofcertain of the ducts;

Fig. 6 is a view similar to Fig. 3 looking in the direction of thearrows 66, Fig. 2;

Fig. 7 is a view similar to Figs. 3 and 6 looking in the direction ofthe arrows 77, Fig. 4;

Fig. 8 is a view similar to Fig. 7 taken on the line 88, Fig. 4;

Fig. 9 is a fragmentary vertical section looking in the direction of thearrows 99, Fig. 4; and

Fig. 10 is a fragmentary vertical section looking in the direction ofthe arrows ilk-10, Fig. 2.

Similar numerals refer to similar parts throughout the various figuresof the drawings.

The improved forced circulation cooling apparatus is F mounted in thefurnace walls.

,. furnace chamber is illustrated in shown somewhat diagrammatically inFig. l incorporated in a continuous strip bright annealing furnacegenerally indicated at 1. The furnace 1 may include a flame heating zonegenerally indicated at 2, a heating zone generally indicated at 3, asoaking zone generally indicated at 4, a controlled cooling zonegenerally indicated at 5, a pipe coil cooling zone generally indicatedat 6, a forced circulation cooling zone generally indicated at I, and anexit 8.

The continuously moving strip to be treated is indicated at 9 and passesfrom a roll or other equipment (not shown) over a guide roll 10 to enterthe flame heating zone 2. The strip 9 then threads back and forth overupper and lower guide or conveyor rolls l1 and 12 in the variouschambers of the furnace so as to pass to and fro through said chambersor compartments. During such travel the strip 9 moves successivelythrough the zones 2, 3, 4, 5, d and 7 to the furnace exit 8. it then maypass under guide roll 13 to a coiler (not shown) or other desiredhandling or treating equipment.

The strip 9 may, for example, be a cold rolled steel strip 0.010 thickand 30" or more wide, used for the manufacture of tinplate; and thebright annealing opera tion to which the strip is subjected in furnace 1may be carried out at strip speeds as high as 1000 F. P. M. However,other gauges and widths of strip material may be treated in the furnace1 at other speeds than indicated.

in subjecting the continuously moving strip 9 to a bright annealingoperation the heating, soaking and initial cooling steps are performedat suitable temperatures for suitable periods of time to obtain thedesired metallurgical results. Thus, as shown, the strip may make threepasses through the heating zone 3, five passes through the soaking zone4, live passes through the controlled cooling zone 5, two passes throughthe pipe coil cooling zone 6, and fourteen passes through the forcedcirculation cooling zone 7 before it emerges through the furnace exit Sinto the atmosphere. it is to be understood that the number andcharacter of zones, and the number of passes in each zone, may be variedin accordance with the character of heat treatment desired and thegauge, width, speed and type of material treated.

The furnace heating and cooling chambers are maintained filled with asuitable special or controlled atmosphere, supplied from any suitablesource in a usual manner, to prevent oxidation of the strip surfacesduring the annealing or heat treatment.

In the example given, the strip temperature may be approximately 900 F.as it leaves the pipe coil cooling zone 6 and this strip temperaturemust be reduced to approximately 200 F. before the strip leaves thecontrolled-atmosphere-filled furnace chamber at exit 3, for otherwiseoxidation of the strip surfaces would result on exposure of the strip tothe atmosphere.

The furnace 1 may be constructed in any suitable or usual manner with astructural framework generally indicated at 14, and with refractorywalls and partitions for the chambers formed in the heating and soakingzones 3 and 4. The walls forming the cooling chambers of zones 5, 6 and7 may also be mounted on the structural framework 14 and may be built ofany usual material such as metal plates. The conveyor rolls 11 and 12may also be mounted in a usual manner on the framework 14 or journalledin bearings (not shown) Some of the rolls ll and 12. may be driven, ifdesired, by suitable drive means, power for conveying the strip 9through furnace 1 also being supplied by the coiler.

The furnace may be equipped with suitable fuel burners (not shown) inall zones thereof where it is necessary to supply heat for carrying outthe desired heat treating operation. In the case of a controlledatmosphere furnace for bright annealing where it is necessary tomaintain a special atmosphere in the furnace, these burners may be usualradiant tube fuel burners. However, other usual means of supplying heatto the furnace and of maintaining a controlled atmosphere in the furnacemay be used where desired.

When strip metal is continuously annealed at speeds as high as 1000 F.P. M., as much as 1700 or more feet of strip must be in the furnaceheating and cooling chambers in order to satisfy the required heatingand cooling cycle. A compact and space saving furnace arrangementenabling such lennth of strip to be in the l in hich the strip passesvertically up and down or to and fro within '7 using water as theultimate cooling means and without requiring special refrigeration orother similar equipment for cooling the cooling medium circulated in theforced circulation system.

Another important feature of the present invention is the provision forlongitudinal flow of the circulating cooli-ng medium which enables thecross sectional area of the stream to be kept small whereby a largestrip area is served by relatively small cubic feet per minute flow ofcooling medium. This in turn means that the blowers may be relativelysmall and the power requirements for the blowers correspondingly smalLStill another important feature of the present invention is that becauseof the closed circulation system charactor of the means for circulatingcooling medium and the 50% parallel flow and 50% counterfiow of thecooling medium with respect to strip travel, the pressures at theentrance and exit ends of the forced circulation cooling zone 7 areinherently balanced so that flow of air into the cooling chamber or lossof special atmosphere from the cooling chamber are avoided. This isfrequently a problem in the provision of forced circulation for eitherheating or cooling a furnace structure because usually, since pressuredifference is necessary to produce flow, there are pressure differencesbetween the entrance and exit ends of a chamber in which forcedcirculation is provided.

It is'iusual practice cooling by forced circulation to pass a stream ofgas first in contact with the surfaces to be cooled and then throughcooling coils. In contrast, another important feature of the presentinvention is that the circulating gas stream passes simultaneously incontact both with the surfaces to be cooled and with the cold platesurfaces which in turn cool the cooling medium. In this manner noadditional space is needed for coil chambers and the over-all size ofthe apparatus is greatly reduced.

Referring to Figs. 2 and 5, in order to gain access to the conveyorrolls .and for threading the furnace, the top wall of the cooling :zonemay be formed by a series of plates 43 having partition walls 18integral therewith, and the plates 43 may be flanged for providing aliquid seal 44 between adjacent plates. Similarly, the bottom wall ofthe cooling zone 7 may have removable liquid sealed plates 45 forpermitting access to the lower conveyor rolls 12 and 12a.

Accordingly, the present invention provides a new and different forcedcirculation cooling apparatus for a continuous strip furnace whichincorporates the new and advantageous features described, overcomesprior art difiiculties, and solves long standing problems in the art.

In the foregoing description certain terms have been used for brevity,.clearness and understanding, but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art because suchterms are utilized for descriptive purposes herein and not for thepurpose of limitation and are intended to be broadly construed.

Moreover, the description of the improvements is by way of example, andthe scope of the invention is not limited to the exact detailsillustrated and described.

Having now described the various features, discoveries and principles ofthe invention, the construction and the operation of .a preferredapparatus arrangement, and the advantageous, new and useful resultsobtained thereby; the new and useful discoveries, principles, apparatus,combinations, parts, subcombinations and elements, and mechanicalequivalents obvious to those skilled in the art, are set forth in theappended claims.

I claim:

1 Apparatus for cooling continuously moving strip passing to and froover a series of conveyor rolls in a controlled atmosphere chamberincluding, a first duct through which the strip travels, a return ductadjacent and parallel with the first duct, circulating fan meansconnected with said ducts for circulating gaseous cooling medium at highvelocity in a closed circuit through said first duct and then throughthe return duct back to the first duct, the Walls of the first duct oneach side of the strip being formed with water cooled surfaces closelyadjacent the strip, the first and return ducts having a common wall, andthe return duct walls also being formed with water cooled surfaces.

2. Apparatus for cooling continuously moving strip passing to and froover a series of conveyor rolls in a controlled atmosphere chamberincluding walls forming a first duct through which the strip passes,another wall spaced from and parallel with one of said first duct wallsforming a return duct, a partition wall transverse the return duct wallsand located intermediate the ends of said first and return duct walls,circulating fan means having an inlet communicating with the return ductat one side of said partition wall and having an outlet communicatingwith the return duct at the other side of said partition wall, saidcirculating fan means discharging controlled atmosphere into said returnduct through said inlet and withdrawing controlled atmosphere from saidreturn duct through said outlet; manifold means connected with one endof the first and return ducts, said manifold means including wallsforming an opening between the return duct and the first duct on oneside of the strip, said manifold means also including walls forming acommunication between said return duct and the first duct on the otherside of the strip; means communicating between the other end of thereturn duct and the other end of the first duct on both sides of thestrip, and cooling surface means associated with Walls of the first ducton either side of the strip throughout the length of strip travel in thefirst duct.

3. Apparatus for cooling continuously moving strip passing to and froover a series of conveyor rolls in a controlled atmosphere chamberincluding walls forming a first duct through which the strip passes,other walls spaced from and parallel with said first duct Walls forminga second duct in which the strip passes in the opposite direction,certain of said first and second duct walls forming a return ductbetween and parallel with said first and second ducts, a partition walltransverse the return duct and located intermediate the ends of saidreturn duct walls, circulating fan means having an inlet communicatingwith the return duct at one side of said partition wall and having anoutlet communicating with the return duct at the other side of saidpartition wall, said circulating fan means discharging controlledatmosphere into said return duct through said inlet and withdrawing theatmosphere from said return duct through said outlet; manifold meansconnecting one end of the return duct with one end of the first andsecond ducts, said manifold means including Walls forming openingsbetween the return duct and the first and second ducts on one side ofthe strip, said manifold means also including walls forming acommunication between the said return duct and the first and secondducts on the other side of said strip; means communicating between theother end of the return duct and the other end of the first and secondducts on both sides of the strip, and cooling surface means associatedwith the walls'of the first and second ducts on either side of the stripthrough out the length of strip travel in said first and second ducts.

4. Apparatus for cooling continuously moving strip passing to and froover a series of conveyor rolls in .a controlled atmosphere chamberincluding walls forming a first duct through which the strip passes,other walls spaced from and parallel with said first duct walls forminga second duct in which the strip passes in the opposite direction,certain of said first and second duct walls forming a return ductbetween and parallel with said first and second ducts, .a partition walltransverse the return duct and located intermediate the ends of saidreturn duct walls, circulating fan means having an inlet communicatingwith the return duct at one side of said partition wall and having anoutlet communicating with the return duct at the other side of saidpartition wall, said circulating fan means discharging controlledatmosphere into said return duct through said inlet and withdrawing theatmosphere from said return duct through said outlet; manifold meansconnecting one end of the return .duct with one end of the first andsecond ducts,

said manifold means including walls forming openings between the returnduct and the first and second ducts on one side of the strip, saidmanifold means also including walls forming a communication between saidreturn duct and the first and second ducts on the other side of saidstrip; said fan means connected with the ducts for circulatingcontrolled atmosphere at high velocity in a closed circuit through oneof said ducts on both sides of the strip in the direction of striptravel and through the other duct on both sides of the strip in adirection opposite that of the strip travel, means communicating betweenthe other end of the return duct and the furnace chambers and zones.However, it is to be understood that the path of travel or passes ofstrip back and forth through the furnace chambers may be arranged to behorizontal rather than vertical. The vertical pass arrangement, however,is preferable since it avoids any necessity for supporting saggingportions of the strip between conveyor rolls at the ends of passes.

In accordance with the present invention improved forced circulationcooling means are provided in the zone 7 for rapidly cooling the stripfrom approximately 900 F. to approximately 200 F. in such zone. In orderto provide for such forced circulation cooling of the strip as it passesto and fro over the upper conveyor rolls 11 and under the lower conveyorrolls 12 in zone 7, a series of ducts are formed in the cooling chamber,one duct for each strip pass either up or down. These ducts are formedby providing a series of partition walls laterally across the furnacechamber.

Referring particularly to Figs. 2, 3, 4 and 5, the first partition wallat the left-hand side of zone 7 is indicated at 15 and extends from thebottom of the furnace chamber (Fig. 5) to just beneath the conveyor roll11a which is the entry conveyor roll for zone 7. Partition wall 15 alsoextends cross-wise of the furnace chamber between side walls 16 and 17.Immediately above conveyor roll 11a, a batlle plate or wall 18 extendsdownward from the roof of the furnace and between side walls 16 and 17to reduce to a minimum anv communication between the cooling zones 6 and7. Thus there is only sufficient space between the top end 15a ofpartition wall 15 and the bottom of battle wall 18 to accommodate roll11a and permit the strip 9 to pass over roll 11a into zone 7.

Spaced to the right of partition wall 15 is another partition wall 19which extends upward from just above the first lower conveyor roll 12ain zone 7 nearly to the top of the cooling chamber as indicated at 19a.The partition wall 19 likewise extends laterally between furnace sidewalls 16 and 17. Another partition wall 20, similar to partition wall 19but spaced to the right thereof (Fig. 2), extends upward from just abovelower conveyor roll 12a to near the roof of the cooling chamber asindicated at 20a. Partition walls 19 and 20 are joined at the top bvwall member 21 extending from the top ends 19a and 20a thereof.

Another partition wall 22 spaced to the right of partition wall 20extends upward from the bottom of the coolin chamber and between chamberside walls 16 and 17. Still another partition wall 23 similar topartition wall 22 is provided spaced to the right of partition wall 22:and walls 22 and 23 are ioined at the t o by wall portion 23a and at thebottom by wall portion 23b. Partition wall portion 23a is similar topartition wall portion 15a and partition wall 23b is similar to thelower end of partition wall 15.

The foregoing arrangement of partition walls is repeated throughout theremainder of the forced circulation cooling zone 7, as shown.

Referring to Figs. 2, 4 and 5, a down-duct 24 is formed betweenpartition walls 15 and 19 through which the strip 9 passes in downwardtravel, and n up-duct 25 is formed between partition walls 20 and 22 thrugh which the s rip passes in upward travel. Intermediate to andparallel with the ducts 24 and 25, a return duct 26 is formed betweenwalls 19 and 20. As shown in Fig. 5, both of the ducts 24 and 25communicate at their b ttom ends directly wi h the b ttom end f returnduct 26.

The upper ends 19a and 20a of partiti n wa ls 19 and 20, a ng ithconnecting top wall member 21, f rm a manifold 27 for the upper end ofreturn duct 26. A slotted opening 1% is formed in wall portion 190 whichestablishes communication between manifold 27 and down-duct 24 on the riht-hand side of the strip portion 9 passing downward through duct 24. Asimilar sl tted opening 20b is formed in wall portion 20a estab ishingcommunication between manifold 27 and up-duct 25 on the left-hand sideof the strip portion 9 passing upward through duct 25.

An opening 28 is formed in the side wall 17 connected with the centralstem 29 of secondary manifold 30 located on the outer side of side wall17. Manifold 30 is provided with two end stems 31 and 32, the stem 31communicating through opening 33 in side wall 17 with the upper end ofdown-duct 24 on the left-hand side of strip 9 passing downward throughduct 24; and stem 32 similarly communicates through opening 34 formed inside wall 17 with the upper end of up-duct 25 on the righthand side ofstrip 9 passing upward in duct 25. In this manner, the upper end ofreturn duct 26 communicates with the upper ends of ducts 24 and 25 onboth sides of the strip passing therethrough.

As shown in Figs. 4 and 9, a cross partition member 35 is providedintermediate the ends of duct 26 extending between partition walls 19and 20 and side walls 16 and 17. An opening 36 is formed in side wall 17below cross partition wall 35 communicating with return duct 26. A fanor blower intake duct 37 communicates with opening 36 and leads to theintake of centrifugal blower 38 driven by motor 39 (Fig. 9). The bloweroutlet communicates by duct 40 with an opening 41 formed in side wall 17communicating with return duct 26 above cross partition wall 35.

By these means, when the blower is operating, there is forcedcirculation of the controlled atmosphere filling the chambers of thefurnace, the gases circulated acting as a cooling medium for the strippassing through ducts 24 and 25. Thus, as shown by the arrows in thedrawings, the cooling medium discharged from blower 38 passes throughduct 40 into return duct 26 above partition wall 35, thence upward induct 26 to manifold 27 where the gas flow divides into four streamsthrough openings 1% and 20b and secondary manifold 30. These fourstreams are delivered to the top ends of ducts 24 and 25 on both sidesof the strip. The cooling medium then circulates downwardly in bothducts 24 and 25 to the lower ends thereof where the flow merges and isdrawn into the lower end of duct 26 (Fig. 5) from whence the coolingmedium flows upwardly in return duct 26 to the intake duct 37 of blower38.

The blowers 38 are operated to circulate the cooling medium at highvelocity so that the latter effectively and eificiently cools the stripby convection. It will be appreciated that while the greatest coolingeffect can be obtained if the cooling medium is circulated at all timesin the direction opposite to the direction of strip travel, neverthelessit would be difficult to provide for such cooling medium flow along thestrip travelling to and fro in the cooling chamber shown.

The structure of the present invention provides a compromise in whichthe circulated cooling medium flows in a direction opposite to thedirection of strip travel in the tip-ducts 25 and in the same directionas the direction of strip travel in the down-ducts 24.

The cooling arrangement of the present invention further involves theprovision of means for cooling the cooling medium that is circulated ina closed system by each blower 38. For this purpose, the partition walls15, 19, 20, 22 and 23 are each formed as cold plate surfaces. Preferablysuch a cold plate surface is provided by using plate coil material whichcomprises two metal sheets having matched corrugations formed thereinproviding an internal passageway through which water may be circulated.These water circulation passages are indicated generally in the drawingsat 42 and may be connected in any desired or usual manner with a sourceof cold water supply and with a warm water outlet.

Alternatively, the cold plate surfaces may be formed by spaced sheetsforming a water jacket through which water may be circulated. As anotheralternative, the partition walls may be formed of single thickness sheetmetal and usual pipe coils through which water is circulated may bemounted thereon in duets 24 and 25 on both sides of the strip and alongthe inside of the walls of ducts 26.

By forming the partition walls as cold plate surfaces in any of themanners indicated, the cooling medium being circulated at high velocitythrough the ducts 24, 25 and 26 passes along the cold plate surfaces athigh velocity and is cooled by convection by the cold plate surfaces notonly at the same time that the circulating cooling medium is cooling thestrip in ducts 24 and 25 but also in its travel through return duct 26.

The cold plate surfaces provided by the partition walls in addition toextracting heat from the circulating cool ing medium, which in turncools the strip, also have some direct cooling effect upon the stripbecause of the close proximity of the cold plate surfaces to the stripin each pass.

By these means, very rapid, efiicient and effective cool.- ing of thestrip is obtained so that the strip may be quickly cooled in the coolingzone 7 from say 900 F. to 200 F.

the other end of the first and second ducts on both sides of the strip,and cooling surface means associated with the walls of the first andsecond ducts on either side of the strip throughout the length of striptravel in said first and second ducts.

5. Apparatus for cooling continuously moving strip including wallsforming a cooling chamber, conveyor rolls for continuously moving thestrip to and fro through said chamber, there being strip entrance andexit openings for said chamber, a first duct in said chamber throughwhich the strip travels in one direction from one conveyor roll to asecond conveyor roll, a second duct in said chamber through which thestrip travels in the opposite direction from said second conveyor rollto a third conveyor roll, a return duct between and parallel with thefirst and second ducts and including manifold means at one end formaking communication between the return duct and one end of said firstand second ducts on both sides of the strip, a partition Wall transverseof the return duct, the return duct having an inlet on one side of thepartition wall and having an outlet on the other side thereof; fan meansconnected with the inlet and outlet for circulating controlledatmosphere cooling medium at high velocity in a closed circuit from saidinlet through the return duct, then through one of said first and secondducts on both sides of the strip in the direction of strip travel andthrough the other of said first and second ducts on both sides of thestrip in a direction opposite that of strip travel, and then from thefirst and second ducts in a common closed path through said return ductto said outlet; means associated with the first and second ducts closelyadjacent each side of the strip throughout the length of the ducts forsimultaneously cooling said strip and said cooling medium as the striptravels through said first and second ducts and as the cooling mediumcirculates through said ducts in said closed circuit and cools the striptraveling therethrough; and said first and second ducts and said returnduct and the fan means therefor Which form said closed circuit beingrepeated in said cooling chamber to form a plurality of closed coolingmedium circulation circuits along the path of strip travel as the stripmoves continuously to and fro over the conveyor rolls through saidcooling chamber.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 939,685 Groom Nov. 9, 1909 2,345,181 Cooper et al. Mar. 28,1944 2,369,748 Nachtman Feb. 20, 1945 2,573,019 Hess Oct. 30, 1951

